Update CHANGELOG

Refs IOS-1728

Author: laevandus

CHANGELOG.md

@@ -3,6 +3,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 # Upcoming
 
+## StreamChatCommonUI
+### ✅ Added
+- Expose customisable layout tokens on `Appearance.tokens` — `DesignSystemTokens` values (radii, padding, sizing, elevation) are now settable [#4114](https://github.com/GetStream/stream-chat-swift/pull/4114)
+
 ## StreamChatUI
 ### 🐞 Fixed
 - Fix attachment upload overlay text and action buttons being illegible in dark mode [#4111](https://github.com/GetStream/stream-chat-swift/pull/4111)